Hammermill hammer and assembly

ABSTRACT

An elongated hammermill hammer having an opening therethrough provided with a bearing wall portion disposed closest to one end of the hammer and of the shape of a portion of the curved surface of a cylinder for receiving a cylindrical hammermill attachment rod snugly thereagainst to provide a greater bearing surface to extend hammer life, the opening further having an access wall portion disposed closer to the other end of the hammer than the bearing wall portion, the access wall portion defining a part of the opening which is of larger area than that defined by the bearing wall portion for a more free reception of the access wall portion on the rod.

United States Patent Jacobson et al.

[ 1 Aug. 8, 1972 [54} HAMMERMILL HAMMER AND ASSEMBLY [72] Inventors:Calvin L. Jacobson, 1421 Onyx Drive, Harlan, Iowa 51537; Robert E.Morken, 3818 Douglas Drive, Crystal, Minn. 55428; Norman C. Silver, 8212So. Virginia Circle, St. Louis Park, Minn. 55426 [22] Filed: Sept. 17,1969 [21] Appl. No.: 858,683

52 US. Cl ..241/195 [51] Int. Cl ..B02c 13/28 [58] Field of Search..241/194, 193, 197, 196, 195

[56] References Cited UNITED STATES PATENTS FOREIGN PATENTS ORAPPLICATIONS Larson 241/195 Austria ..'...241/194 277,595 9/1927 GreatBritain ..24l/ 196 Primary Examiner-Andrew R. J uhasz AssistantExaminer-Michael Koczo, Jr.

Attorney-Hiram A. Sturges [5 7] ABSTRACT An elongated harnmermill hammerhaving an opening therethrough provided with a bearing wall portiondisposed closest to one end of the hammer and of the shape of a portionof the curved surface of a cylinder for receiving a cylindricalharnmermill attachment rod snugly thereagainst to provide a greaterbearing surface to extend hammer life, the opening further having anaccess wall portion disposed closer to the other end of the hammer thanthe bearing wall portion, the access wall portion defining a part of theopening which is of larger area than that defined by the bearing wallportion for a more free reception of the access wall portion on the rod.

5 Claims, 5 Drawing Figures PATENTEDA B 8 I97? 3.882.401

INVENTORS Fl G 4 CALVIN L. JACOBSON ROBERT E. MORKEN BY NORMAN c. SILVERHAMMERMILL HAMMER AND ASSEMBLY FIELD OF THE INVENTION This invention isin the field of hammermill installations for grinding grain and otherproducts, and particularly in installations in which a rotor rotates atbetween 1, 200 and 3, 600 revolutions per minute.

DESCRIPTION of THE PRIOR ART Serious trouble has been experienced withthe cracking off of the ends of hammermill hammer when the rotorrevolutions per minute are as described, the most serious troubleoccurring when the revolutions per minute are between 3, 000 and 3, 600.

In the past, the openings in hamrnerrnill hammers have commonly beenpunched or drilled of cylindrical shape. However, such openings have haddiameters substantially greater than the diameter of the hammerattachment rod, as has been necessary to provide a looseness of fitenabling the hammer to be slid along a rod with ease to keep the labortime required for installation at a minimum.

As a result, the part of a prior art hammer opening wall surface whichactually touches and bears against the rod is of very, very small area.This can be best understood when considering that in theory, twocylinders of different diameters can be tangent to one another onlyalong a single thin line.

The pressure along this thin line is concentrated and is extremely greatand even after a certain amount of wear in when the line has become asmall thin area the force is very concentrated. The centrifugal forcecauses this pressure, at higher revolutions per minute of the rotor, toexceed the tensile strength of the hammer material, causing cracking.

This cracking spreads from the small thin area of bearing pressureoutwardly until the end of the hammer has cracked away.

The seriousness of this cracking can be easily understood when oneconsiders that the chips or pieces of metal coming from the hammer hitand damage other hammers.

Even one such broken away chip or piece can ruin an entire hammermill,including its fan, as is a most serious possibility.

High labor costs are involved in removing a hammer which is brokenbecause, to reach .it, all hammers on the same end of a rod up to thathammer must be removed.

For this reason, the cost of replacement of a cracked hammer is asubstantial part of the cost of hammermill operation. Also down-time forthis maintenance results in lost production.

Furthermore replacing one hammer with a new one results in the millbeing out of balance because the new hammer weighs more than wornhammers. This can lead to further maintenance problems.

Heretofore no solution to these problems has been found. 7

Since making our invention, we have become informed of an Austrianpatent to Ole Rolfsen, Pat. No. 98012, issued Apr. 15, 1924, showing aspecial triangular hammer. We have never seen a triangularhammer. Themillions of hammers sold each year are almost all of oblong rectangularshape.

The Rolfsen hammer patent teaches an opening formed by three lappingbores of equal diameter.

Before our invention, persons in the industry, Rolfsen himself included,have never conceived of forming a hammer with a two-section hole tosolve the abovestated problems.

SUMMARY OF THE INVENTION An hammermill hammer having an openingtherethrough provided with a bearing wall portion disposed closest toone end of the hammer and of the shape of a a portion of the curvedsurface of a cylinder for receiving a cylindrical hammermill attachmentrod snugly thereagainst to provide a greater bearing surface to extendhammer life, the opening further having an access wall portion disposedcloser to the other end of the hammer than the bearing wall portion, theaccess wall portion defining a part of the opening which is of largerarea than that defined by the bearing wall portion for a more freereception of the access wall portion on the rod, all points on theaccess wall portion being spaced from respective points on the bearingwall portion, which latter are disposed directly across the opening fromeach bearing wall point by a spacing distance greater than the diameterof the curved surface of the bearing portion whereby the access wallportion defines a part of the opening which is of larger area as seenwhen looking therethrough than the portion bounded by the bearing wallportion for more free reception on the rod than is the case with thebearing portion itself.

The bearing wall portion being of a shape of not more than half of thecurved surface of a cylinder for permitting the rod to pass into thatpart of the opening which is bounded partly by the bearing wall portion.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary sideelevational and part sectional view showing our improved hammer mountedon the rotor of a hammerrnill.

FIG. 2 is a frontal elevation of one of the thin sides of our hammer.

FIG. 3 is a side elevation of an end portion of our hammer.

FIG. 4 is a end view of our hammer.

FIG. 5 is a secu'onal view of FIG. 1 as taken along the line 5-5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The elongated hammer of thisinvention is generally indicated at 10 and is shown as mounted on ahammermill generally indicated at 12 and having a rotor generallyindicated at 20 which rotates about an axis,

5 not shown, in a common manner within a cylindrical screen, a part ofwhich is shown at 24.

The hammer 10, as well as other hammers, not shown, are attached to therotor 20 by an attachment rod 30.

The rod 30 is always horizontally disposed and is of cylindrical shape.

In accordance with this invention, the hammer 10 is provided with aspecial opening 40 which extends transversely through the thickness ofthe hammer 10, the hammer 10 having a greater width than thickness.

The opening 40 has a wall 42 having a concave bearing wall portion 50disposed closest to one end 54 of the hammer. The bearing wall portion50 is for the purpose of snugly bearing against the cylindrical rod 30which extends therethrough for securing the hammer to the rotor 20.

The bearing portion 50 is substantially of the shape of a portion of thecurved surface of a as the outer surface of the rod 30 for closelyfitting the rod 30.

The opening 40 further has an access wall portion 70 disposed closer tothe other end 74 of the hammer than is the bearing wall portion 50.

All points on the access wall portion 70 are spaced from respectivepoints on the bearing wall portion 50, which latter are disposed spaceddirectly across the opening 40 from each bearing wall point by a spacingdistance greater than the diameter of the curved surface of the bearingwall portion 50, whereby the access wall portion 70 defines a part ofthe opening which is of larger area as seen when looking therethrough,as in FIG. 3, than the portion bounded by the bearing wall portion 50for more free reception of the hammer on the rod than would be the caseif the opening 40 were of the size of the bearing wall portion 50itself.

The bearing wall portion 50 is of the shape of not more than half of thecurved surface of a cylinder for permitting the rod to pass into thatpart of the opening 40 which is bounded partly by the bearing wallportion 50.

As best seen in FIG. 3, the access wall portion 70 can also be of theshape of the curved surface of a cylinder, although the diameter of theshape of the access wall portion 70 is greater than the diameter of thecurvature of the bearing wall portion 50.

As best seen in FIG. 1, the hammer further has a second and identicallydefinable opening 90 at the other end thereof and arranged so that thebearing surfaces of each opening are closest to the opposite ends of thehammer respectively, whereby in FIG. 2 the bearing surface of theopening 90 is at 94.

The ends of the bearing wall portion 50 are substantially equidistantfrom a line 100 extending through the center of gravity 102 of thehammer and through the center of the bearing wall portion 50.

The bearing wall portion 50 of the hammer should be of soft enoughmaterial to permit wear in to obtain good contact with the rod tocompensate for manufacturing imperfection and it should be hard enoughto give sufficient strength. We have found the hardness level of R 38-48to be satisfactory. Where there is considerable manufacturingimperfection and an excessive hardness then there might be highconcentrated stresses in small areas because of inadequate contactbetween the bearing surface and the rod give rise to premature failures.

It is to be realized however that wear in alone is not a substitute forstriving to have the bearing surface substantialiy cylindrical because atapered bearing side surface, for example, one which is substantially aportion of a frustro-conical configuration such as would be formed bypunching the recess with a punch and with an identically sized dieopening, would be much interiall'd.FIG.5h h odO t r ted tliiot l gh manylia ers lb as is a ri d done with high labor cost in the prior artwhenever the rod-to-hammer-hole fit was snug, and as made easy by theenlarged hole 40 of this invention, accomplished with good rod-fit atbearing wall portion 50 of radius of arc-radius equal to the radius ofthe rod 30, which is cylindrical, for long hammer life and distributedpressure.

The reason high labor costs are involved with a snug or tight-fittinghammer hole is that sliding such hammers along a rod is difficult andthere are so many hammers to put in place or remove.

We claim:

1. An elongated hammermill hammer of greater width than thickness andhaving an opening transversely through the thickness thereof, saidopening having a wall having a concave bearing wall portion disposedclosest to one end of said hammer, said bearing wall portion being forthe purpose of snugly bearing against a cylindrical rod extended throughsaid opening and securing said hammer to a harnmerrnill rotor, saidbearing wall portion being substantially of the shape of a portion ofthe curved surface of the cylinder for closely fitting said rod, saidopening wall further having an access wall portion disposed closer tothe other end of said hammer than said bearing wall portion, all pointson said access wall portion lying substantially on a cylindricalconfiguration and being spaced from respective points on said bearingwall portion which latter are disposed spaced directly across saidopening from each bearing wall point by a spacing distance greater thanthe diameter of said curved surface of said bearing wall portion wherebysaid access wall portion defines a part of said opening which is oflarger area as seen when looking therethrough than the portion boundedby said bearing wall portion for more free reception on said rod thansaid bearing wall portion.

2. The combination of claim 1 in which said hammer further has a secondand identically definable opening at the other end thereof and arrangedso that the bearing surfaces of each opening are closest to oppositeends of the said hammer respectively.

3. The hammer .of claim 1 in further combination with multiple similarhammers disposed alongside said first hammer, and in combination withsaid cylindrical rod extending through the respective ones of saidopenings of said multiple hammers.

4. The combination of claim 1 in which the ends of said bearing wallportion are substantially equidistant from a line extending through thecenter of gravity of the hammer and through the center of said bearingwall portion.

5. The combination of claim 1 in which said hammer is formed of platematerial having large flat parallel sides and in which said bearing wallportion extends at a right angle to the large flat parallel sides of thehammer.

1. An elongated hammermill hammer of greater width than thickness andhaving an opening transversely through the thickness thereof, saidopening having a wall having a concave bearing wall portion disposedclosest to one end of said hammer, said bearing wall portion being forthe purpose of snugly bearing against a cylindrical rod extended throughsaid opening and securing said hammer to a hammermill rotor, saidbearing wall portion being substantially of the shape of a portion ofthe curved surface of the cylinder for closely fitting said rod, saidopening wall further having an access wall portion disposed closer tothe other end of said hammer than said bearing wall portion, all pointson said access wall portion lying substantially on a cylindricalconfiguration and being spaced from respective points on said bearingwall portion which latter are disposed spaced directly across saidopening from each beAring wall point by a spacing distance greater thanthe diameter of said curved surface of said bearing wall portion wherebysaid access wall portion defines a part of said opening which is oflarger area as seen when looking therethrough than the portion boundedby said bearing wall portion for more free reception on said rod thansaid bearing wall portion.
 2. The combination of claim 1 in which saidhammer further has a second and identically definable opening at theother end thereof and arranged so that the bearing surfaces of eachopening are closest to opposite ends of the said hammer respectively. 3.The hammer of claim 1 in further combination with multiple similarhammers disposed alongside said first hammer, and in combination withsaid cylindrical rod extending through the respective ones of saidopenings of said multiple hammers.
 4. The combination of claim 1 inwhich the ends of said bearing wall portion are substantiallyequidistant from a line extending through the center of gravity of thehammer and through the center of said bearing wall portion.
 5. Thecombination of claim 1 in which said hammer is formed of plate materialhaving large flat parallel sides and in which said bearing wall portionextends at a right angle to the large flat parallel sides of the hammer.